CCD imager output signal processing using drain output signal and wide-band sampled detected floating-element output signal

Abstract

First and second output signals are taken from a floating element in a CCD charge transfer channel and from the terminal drain diffusion of that CCD charge transfer channel. The floating element is part of an electrometer, and the electrometer response is wide-band sampled at the CCD charge transfer channel clocking rate. Current flow through the terminal drain diffusion is sensed by the input circuit of a low l/f noise transresistance amplifier. Continuous-frequency-spectrum low-noise output signal is generated from the low-frequency components of the transresistance amplifier response and from the high-frequency components of the processed second output signal. Subsequent filtering removes unwanted clock and aliased frequency components.

What is claimed is: 
     
       1. In combination with a solid-state imager having an output charge-coupled device charge transfer channel clocked at a prescribed clock rate, having a floating element electrometer for sensing charge at a point in said charge transfer channel to supply a first signal at a first electrical output, and having a terminal drain at the end of said charge transfer channel for supplying a further signal at a second electrical output, circuitry for generating an output video signal responsive to the signals at said first and second electrical outputs comprising: means for deriving the high-frequency portion of said output video signal, said deriving means including means coupled to said first electrical output for providing wide-band multiple sampling of the video information portion of said first signal, which wide-band sampling is associated with the generation of undesirable low-frequency-fixed pattern shading;   means for deriving the low-frequency portion of said output video signal from said further signal at said second electrical output; and   means for combining the low-frequency and high-frequency portions of said output video signal into a continuous-frequency-spectrum signal.   
     
     
       2. In combination with a solid-state imager having an output charge-coupled device charge transfer channel clocked at a prescribed clock rate, having a floating element electrometer for sensing charge at a point in said charge transfer channel to supply a first electrical output signal, and having a terminal drain at the end of said charge transfer channel for supplying a second output signal, circuitry for generating an output video signal responsive to said first and second electrical signals comprising: means for deriving the high-frequency portion of said output video signal from said first electrical output signal after wide-band sampling thereof, which wide-band sampling is associated with the generation of undesirable low-frequency-fixed pattern shading;   means for deriving the low-frequency portion of said output video signal from said second electrical output signal;   means for combining the low-frequency and high-frequency portions of said output video signal into a continuous-frequency-spectrum signal; and   said means for deriving the high-frequency portion of said output signal includes:   a low-frequency-suppresion filter, with an input connection receptive of said first electrical output signal from said solid-state imager, and with an output connection; and   a synchronous detector having an input connection from the output connection of said low-frequency-suppression filter, performing said wide-band sampling at a harmonic of said prescribed clock rate, and having an output connection; and   a filter separating the high-frequency portion of response at the output connection of said synchronous detector, for application to said means for combining.   
     
     
       3. In combination with a solid-state imager having an output charge-coupled device charge transfer channel clocked at a prescribed clock rate, having a floating element electrometer for sensing charge at a point in said charge transfer channel to supply a first electrical output signal, and having a terminal drain at the end of said charge transfer channel for supplying a second output signal, circuitry for generating an output video signal responsive to said first and second electrical signals comprising: means for deriving the high-frequency portion of said output video signal from said first electrical output signal after wide-band sampling thereof, which wide-band sampling is associated with the generation of undesirable low-frequency-fixed pattern shading;   means for deriving the low-frequency portion of said output video signal from said second electrical output signal;   means for combining the low-frequency and high-frequency portions of said output video signal into a continuous-frequency-spectrum signal; and   said means for deriving the high-frequency portion of said output signal includes:   correlated double sampling apparatus for wide-band sampling said first electrical output signal from said solid-state imager; and   a filter separating the high-frequency portion of the correlated double sampled first electrical output signal, for application to said means for combining.